In the Internet of Things (IoT) field, development in various fields such as goods management using machine to machine (M2M) and healthcare using a body area network (BAN) has been expected.
Time division multiple access (TDMA) is one of communication methods that may be used in IoT. For example, there is a network in which a wireless base station (called a “hub”) performs wireless communication with a plurality of wireless terminals (called “nodes”) using TDMA. In the description below, a wireless base station is simply indicated as “base station”, and a wireless terminal is simply indicated as “terminal”.
In TDMA, time is divided in units of a predetermined time length called frames, and each frame is further divided in units of time of a predetermined length (called “time slots”). The base station assigns time slots to the respective terminals. Each terminal transmits information to the base station using the time slots assigned to the terminal. Consequently, even if a same frequency bandwidth is shared between the terminals, each terminal can transmit information to the base station with no interference.
The base station manages the frames and the time slots, and in response to a connection request from each terminal, searches for time slots in an empty state (empty slots) and assigns the time slots. Here, a bandwidth the terminal desires to use in communication is expressed by the number of time slots the terminal desires to use.
In empty slot assignment, if the communication cycles and the bandwidths (time slot counts) the terminals desire to use are the same, the base station can assign arbitrary empty slots to the respective terminals. A communication cycle is, for example, a cycle of transmission of information by a terminal.
For further information, see Japanese Laid-Open Patent Publication No. 2008-187463, Japanese Laid-Open Patent Publication No. 2008-271376, Japanese National Publication of International Patent Application No. 2005-528014, and Japanese Laid-Open Patent Publication No. 2002-152124.